The invention relates to mufflers, and more particularly to the combination with a water trap for protecting the muffler, particularly a catalytic substrate and matte mounting, during rain or when the vehicle is washed.
The invention arose during development efforts directed toward a diesel exhaust muffler in a transit bus, particularly a soot trap muffler having a catalytic substrate and matte mounting. It is desired to capture water that may enter a vertical exhaust outlet when washing the vehicle or during rain. A water trap serves to protect the catalytic substrate and matte mounting material. Water entry can lead to failure of the matte mounting material and/or plugging of the substrate due to matte erosion.
The existing muffler in the noted transit bus application is an oval vertically mounted muffler having a lower exhaust inlet and a laterally offset upper exhaust outlet. In replacing this muffler with a soot trap muffler, it is desired to provide a round cylindrical vertical exhaust stack, and to prevent entry of water as above noted. The existing muffler was about 30 inches long, or less in some instances. The muffler length and orientation were predetermined by the space constraints of the bus compartment. In the case of a soot trap muffler, the catalyst and/or soot filter adds significant length to the muffler. This additional length in combination with an internal water trap would exceed the length available to fit the muffler into the bus compartment.
Also in the existing oval muffler, the lateral offset between the inlet and outlet was about 9.5 inches. It is desired to maintain this lateral spacing, to facilitate proper exhaust stack alignment and to minimize modifications to existing tubing. It is also desirable that the inlet be laterally centered in the body of the muffler to provide optimum flow distribution across the catalyst face, rather than being laterally offset to one side of the catalyst face.
The present invention addresses and solves the above-noted desired design criteria. The invention has application beyond the noted bus installation.